This Instructable describes how to replace the fan inside a standard PC power supply. You may want to do this because the fan is defective, or to install a different type of fan, for example, an illuminated one.

In my case, I decided to replace the fan because my cheap power supply's fan started making enough noise to drive me to distraction...

  • Power supplies have dangerous voltages inside, even when completely disconnected. Capacitors on the line side usually retain their full charge even when unplugged, and can inflict a painful or even lethal shock. Please proceed only if you know what you are doing.
  • Disassembling the power supply will void its warranty.
  • Opening your PC may void its warranty, though I haven't come across such a computer so far. Also, fiddling with the insides may damage other components, so go ahead only if you are sure of yourself.
- 2011-05-02 : Corrected explanation of fan dimensions. Thanks to KanyonKris for the correction (see comment at bottom)

Step 1: Before you start

You will need to know what kind of fan you need to replace. Obviously, the only way to know this is to open up the power supply and see what type is required. In my case, I had to open it up twice; once to find out the type of fan, and the second time to replace it.

For your safety:
Before opening the power supply, try to discharge the capacitors inside as much as possible. I did this by switching on the PC and unplugging the power cord. Of course, there is no guarantee that this will completely discharge the capacitors.

Another method is to use a 1 megaohm resistor to short the capacitors. The capacitors are the large ones shown in step 6.
<strong>IMPORTANT CORRECTION</strong> - The fan size is is the length along any side of the housing (<strong>L</strong> in image below), <strong>not</strong> the distance between screw holes.<br> <br> For example: a 80mm fan is 80mm across. The distance between screw holes is 71.5mm.<br> <br> Also make sure the width (<strong>W</strong> in image below) of the replacement fan will fit in the power supply. The easiest way to do this is to buy a replacement that has the same width as the old fan.<br>
Thanks for the correction... I could have sworn I actually measured it as 80mm between screw holes. Are you sure it is the same for all fans? Google is being unhelpful today, I still couldn't find a site that actually gives the exact specifications.<br>Still, I think you are right, I'll update the instructable as soon as I find a decent reference to link to.
I'm sure the dimension (ie 80mm) is across the fan body. All the fan manufacturers I know of use these dimensions. The illustration above was taken from <a href="http://mouser.com">Mouser</a>, a large distributor of electronic parts. <a href="http://digikey.com">Digikey</a> is the same.<br> <br> I too was surprised I couldn't quickly find a good source on the web about these fans. If I would have found one I would have included a link. The best I could do was the illustration.
<br> I find that if the fan is really annoyingly noisy, pulling off the label and removing the rubber plug, exposing the bearing (sleeve or ball), then applying a few drops of 3-in-1 oil and letting it settle in virtually silences them, so you get more use out of them and more time to go buy a new fan... :)<br> <br> And yes, do be careful of them capacitors, I have been shocked a couple of times by them, and it hurts, majorly!!! It's like someone stabbing a hot screwdriver into your skin and muscles, it's not something that you'd want to happen, well, not unless you're a weirdo... :S<br>
If your computer is old enough that the fan in the power supply is making noise, it is probably older than the warranty is long. Good Instructable, though. I read one edition of Scott Mueller's <strong>Upgrading and Repairing PCs</strong> and he warned people against ever opening a power supply because of the potentially dangerous voltages, even when disconnected. Still, it would be possible. <br/>
Thanks! Yes, you are right, the warranty has long since expired. I did post warnings about the dangerous voltages inside, but if you are careful, a simple replacement like this shouldn't be too dangerous.
just stay clear of capacitors (they look like cylinders with two wires going into the board), as they can hold high voltages long after the supply is unplugged (years). also be careful about touching the board itself as those leads the capacitors are connected to go somewhere.
To discharge them,short green wire to any black while unplugged.That turns it on only to discharge the caps.
<p>How likely would I be to get a shock from a brand new power supply that<br> I'm sure has set in a distribution center for quite awhile? I have been<br> trying to find a power supply with an orange led fan for a few years <br>now I have contacted several manufacturers asking them if I purchase the<br> fan could they replace it but I have not heard back from them, so I <br>guess I am left with the only option of attempting this myself to finish<br> off my son's &quot;dream machine.&quot;</p>
<p>I'm one that adds engine oil to the fan bearing, and this can last a good long time.</p>
<p>Couldn't you have also just found a dead mobo, removed the two-pin fan header from that and solder on those header pins to make the fan more easily replaceable?</p>
<p>Nice job. Good pictures and explanations.</p><p>I have replaced a couple of PSU fans with good success each time. I much prefer the cost of the fan over the cost of a new PSU.</p>
Sometimes (like with my computer) you can't see all the connections, so you may want to tag the connections by wrapping a &quot;tag&quot; of masking tape to each wire, and writing down where it came from when you disconnect it.
For almost all power supplies, simply connect the green wire to any black wire with any suitable wire or un-coated paperclip straightened, then bent into a &quot;U&quot; shape. <br>Adding a photo doesn't seem to be working, so here's how to know you have the right spot. With the locking tab of the motherboard power connector facing up, and the holes facing towards you, the green wire is always the fourth from the left, and there is a ground (black) wire on either side of it. Simply take a wire with bare ends or an uncurled paperclip, and put one end in the green wire hole, and the other into the hole to either side of it. Connect power to the power supply, and turn on the power switch on the power supply itself if it has one. The power supply should power up, and the fan should spin. If not, disconnect the power cord immediately.
my fan started to be very noisy and just lubing it didn't help then i changed fan and now its really quiet tnx
I ended up using an 80CFM 80mm fan. It sounds like a jet and always blasts out cold air (it more than just does the job).
i am always touching capacitors even when it is powered on, and i am still alive, am i?
You have to touch the leads, not the top of the capacitor, for it to be lethal. Do you ever get a shock?
could I able to ask a question?? its all about power supply!!
well,, thanks a lot,,And now? I fully I understand already.
I would recommend the chop and insulate method, you're right in that it's not as neat but you won't see it inside the PSU housing anyway and it'd be much easier
hi <br>the instructions were so useful <br>iv decided to change my power supply fan because its noisy <br>but Ive bought 220 volt fans to replace them with the old one and connect it directly to the electricity <br>i want the fan not use the voltage generated by the power supply(12 volts) as i thought more voltage will be provided for my other devices <br>I m going to do this, can somebody give me advises on doing this? <br>thank u
You could connect it directly to the AC input of the power supply, but then it will run continuously even when the computer is switched off (unless you switch it off at the plug). <br><br>What is the power rating (Watts) of the supply, and how many devices have you got attached? The fan doesn't draw that much current, you may be OK with a regular 12V fan.<br>
i just got a antec computer with the power supply fan not moving. thanks for the info!
Glad you found it useful!
&nbsp;You forgot&nbsp;say&nbsp;each of&nbsp;those&nbsp;capacitors&nbsp;can still hold a&nbsp;charge&nbsp;of about <strong>200 volts!!</strong>
I did not. Read the warnings at the top.<br /> <br />
Maybe you should have.
Should have what?<br />
I&nbsp;meant&nbsp;you should have read the warnings on the top.
OK... I see the misunderstanding. What I&nbsp;said was, I did not forget to warn about the voltages. Read the warnings at the top of the instructable, that is exactly what I&nbsp;have said. <br /> <br /> By the way, the residual voltages can exceed 400V, depending on the line voltage in your country.<br />
I just took apart a dead PS and the sticker was below the break point.
Nice tutorial! Cutting off the yellow cable on a 3-wire PSU is especially usefull.<br />
Thanks!<br /> <br /> Yes, the yellow wire is the speed sensor, which was not used in my power supply.
ive done plenty of power supply fan surgeries, its pretty easy as long as you do it right. this instructable is pretty straightforward :)
Thanks! :-)
Instead of replacing it you could also just clean and relube it. There's several guides here for that. Reminds me of a story... I have a server in the basement and I rarely touch it and went down one time and noticed the fan in the PS had seized up. Could've been out for months for all I knew. I didnt have the time to fix it so I took another fan and screwed it onto the back of the case over top of the PS vent and plugged it into a hd drive power line. Seemed to work till I got around to replacing it.
Yes, that is a good idea, but I opted for a replacement because the new fan claims a 120,000 hour lifetime (MTBF) and a very low noise rating, which would not be possible if I relubed the same fan (it was a bit noisy from the start). I'll keep in mind your emergency fix, just in case! :-)

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